tnmedic

I went out and started the heep this morning and finally starts. I have a fuel pressure problem I know it leaks down but onto the bigger problem this AM. The radio doesn't come no biggie there well then I notice the defrost fan isn't blowing but its on high and the rear defrost wont come on either. I turned the headlights on to see if they will come on and they did and kicked everything on at that point. Sat there for a few minutes, five at the most and it all shuts off again and stays off this time. Finally about 20 minutes later after I scrap the windows and head to work to pick up my paycheck they come back on. I did pop the hood and wiggled the wiring harnesses under the hood with no results, so I am stumped by this. Any suggestions on where to start looking and how hard is the wiring harness inside the cab to replace if this is the problem? Anyway thanks for any help ahead of time I'm posting this from my phone and the search feature left a lot to be desired. Later tnmedic